Synthesis, structure, properties, and phosphatase-like activity of the first heterodinuclear FeIIIMnII complex with the unsymmetric ligand H2BPBPMP as a model for the PAP in sweet potato

The new heterodinuclear mixed valence complex [(FeMn\\)-Mn-\\\-(BPBPMP)(OAc)(2)]CIO4 (1) with the unsymmetrical N5O2 donor ligand 2-bis[{(2-pyridylmethyl)-aminomethyl}-6-{(2-hydroxybenzyl)-(2-pyridylmethyl)}-aminomethyl]-4-methylphenol (H2BPBPMP) has been synthesized and characterized. Compound 1 crystallizes in the monoclinic system, space group P2(1)/c, and has an (FeMn\\)-Mn-\\\ (mu-phenoxo)-bis(mu-carboxylato) core. Two quasireversible electron transfers at -870 and +440 mV versus Fc/Fc(+) corresponding to the (FeMn\\)-Mn-\\/(FeMn\\)-Mn-\\\ and (FeMn\\)-Mn-\\\/(FeMn\\\)-Mn-\\\ couples, respectively, appear in the cyclic voltammogram. The dinuclear (FeMn\\)-Mn-\\\ center has weakly antiferromagnetic coupling with J = -6.8 cm(-1) and g = 1.93. The Fe-57 Mossbauer spectrum exhibits a single doublet, delta = 0.48 mm s(-1) and DeltaE(Q) = 1.04 mm s(-1) for the high spin Fe-\\\ ion. Phosphatase-like activity at pH 6.7 with the substrate 2,4- bis(dinitrophenyl)phosphate reveals saturation kinetics with the following Michaelis-Menten constants: K-m = 2.103 mM, V-max = 1.803 x 10(-5) mM s(-1), and k(cat) = 4.51 x 10(-4) s(-1).